4
Both tu & vous mean you. Use tu for: a friend, a family member, or someone your own age. Use vous for: more than one person or an adult who is not a family member.

5
The pronoun on has no direct translation in English. It can mean we, they (as in people in general) or one. (Youll know the meaning based on the context.) –En France, on parle français. –In France, they (people in general) speak French.